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Specification forming part of Letters PatenhNo. EQQJE ti, dated December 10, 1 50.

To all. whom it may concern:

Be it known that IQ, GEORGE MATHIOT, 0t .theicity of Washington, in the District of U0- ;lnmbia, have invented a new and improved process 101' preventing the adhesion of the do posit to the recipient in the clectrotype process; and I do hereby declare that the following is a full and exact description thereof.

it is well known that in copyingengraved plates by the el'eetrotype the deposit is apt to adhere so firmly to the original or mold as to resistevery attempt to separate them, the eng'raved plate being thereby destroyed. 1 pre vent this destructive adhesion by making the plate to be copied chemically clean and then expose it to the action of a halogen element or compound; and I further expose the plate so acted on to the action of a strong light for several hours bei'ore introducing it into the electrotyping apparatus.

To enable others skilled in the art a t electrometallurgy to practice and use my invention, 1 will proceed to describemy method ol'daplieating a copper-plate.

5 use a voltaic battery and the usual apparains for duplicatio by the clectrotype; but in order to prevent the danger of the adhesion of the deposit to the plate I first make the plateperfectly clean by methods well known, and then silver the surface by any of the methods well known to electro-metallurgists. I then wash thewatcrfrom the surface with alcohol, and immediately pour over this clean surface of silver a'solution of iodine in strong alcohol. I then incline the plate, so that the fluid may quickly drain off, and expose the plate to sunshine or a bright sky for one or 1110M hours. I then introduce it into the light is not indispensable, but I prefer to silver the plate, that I may have a new surface with a camels-hair' brush.

for the action of the iodine, and also for the action of light on the, iodide oi silver, which causes the plates to separate with "rent case, though by merely washing the plate with the solution ot'iodinc the destructive adhesion will be prevented. a

The ease with which thcplates separalodepends on the intensity of the light and duration oi exposure. When a plate has been merely washed with iodine, or silvcrcd and washed, it" placed in a dark place for several hours and then placed in the precipitatingtrough it may adhere so as to require some force for separation, but the deposit-ed cop per will never be incorporated with the recipient, so as to produce destructive adhesion; but when the plate has been exposed to sun shine so as to become heated there will not be the slightest adhesion.

When the plate to be iodized has a lace as great as ten square Feet the solution of iodine should not be stronger thanone grain ol iodine to t -iienty thousand grains of strong; alcohol. When the plate is smaller than above the solotion may be somewhat stronger, so that for plates of less face than one square foot the solution may consist of one grain of iodine. in seven thousand grains of alcohol. When the plate is first washed with the iodine it may not show it at all, or at most the silver surface acquires a very slight tinge of yellow;

bntin an hour or more, it exposedato l i5 "ht, ,,it.v

will have acquired a leaden appearance, or appear covered with a line dust, similar to the bloom on a plum. When the surface is wanted to be very fine this bloom may be swept on When thisprocess of iodi'zing and lighting has been well exccuted the plate, when examined with a magnifier, presents an iridescent appearance. The same may also be applied by vaporization;

Idonot claim to cover the face of the plate with heterogeneous matters-as air, smoke,

wax, oil, &c.for thepnr-pose ol' prcven-tin9,1,v

adhesion; but- I claim- 1. To form a heterogeneous substanoeon the surface of the metallic plate by exposing it to the action of-iodine, bromine, chlorine, or other chemical capable of forming an insoluble oompound with the motel, for: the purpose herein set forth. i V

2. To expose the metallic plate to the action of light) after being acted on by a halogen element,. substantially for the purpose of preventing the adhesion of the deposit, as specifind.

o. B.- Moss, VILs N M, (LFAIRFA 

